The disclosed technology relates to a method for preparing a nitrogen-containing polymer, useful as a dispersant viscosity modifier, by reacting a melt of a functionalized polymer with a solution of an amine.
Functionalized hydrocarbon polymers such as olefin copolymers are known for use as dispersant viscosity modifiers. Viscosity modifiers in general are polymeric materials, such as ethylene/alpha-olefin copolymers, which, when added to a fluid such as lubricating oil, improve the viscosity index, that is, reduce the change in viscosity of the lubricant as a function of temperature. Certain viscosity modifiers are also designed to contain additional chemical functionality as a part of their structure, in order to impart additional benefits to a lubricant. For instance, relatively polar molecules such as amines or amides may be included to provide a measure of dispersant property to the polymer, which may be used to supplement or replace dispersancy otherwise provided by separate dispersant molecules. In some cases, the relatively polar molecules may be attached to the polymer molecule via a condensation reaction between a primary or secondary amino group and an acid or anhydride group that is a part of the polymer chain or that is appended from the polymer chain, typically through a grafting reaction. Various methods have been suggested for providing such functionalized polymers.
U.S. Pat. No. 6,107,257, Valcho et al., Aug. 22, 2000, discloses highly grafted, multi-functional olefin copolymer which is the reaction product of an acylated olefin copolymer and a polyamine. An acylated ethylene-propylene copolymer was reacted with N-phenyl-1,4,-phenylenediamine in the presence of a surfactant. Typically the polyamine compound is dissolved in a surfactant and added to a mineral or synthetic lubricating oil or solvent solution containing the acylated olefin copolymer. The solution may be heated to 120° to 200° C. It is also possible to add a surfactant solution of the polyamine compound to zones downstream from the graft reaction-vent zones in a twin screw extruder reactor. A suitable class of surfactants includes aliphatic or phenolic alkoxylates. Preferred surfactants contain a functional group, e.g., —OH. Examples include Surfonic® N-40, N-60, L-24-5, L-46-7, Neodol®23-5, 25-7 and Tergitol® surfactants. The total amount of surfactant in the finished additive may be 10 wt. % or less. In an example, an acylated ethylene-propylene copolymer was reacted with N-phenyl-1,4-phenylenediamine, in the presence of a surfactant, at 160° C.
U.S. Pat. No. 8,338,343, Meessen et al., Dec. 25, 2012, discloses (A) a first extruder, grafting olefinic carboxylic acylating agent onto a copolymer; and (b) reacting, in a second extruder, the acylated copolymer made in (A) with a polyamine such a N-arylphenylenediamine. The second step is preferably carried out in the presence of an acid. The polyamine may be dosed to the acylated polymer melt as a melt, solution, or suspension in solvents or oil. A surfactant may be used to solubilize the amine. A second reactor, such as a static mixer, allows substantial conversion of the acylated polymer and the polyamine. The product from the second reactor device is discharged into a connected finishing extruder, which devolatilizes the functionalized polymer product.
U.S. Pat. No. 6,723,796, Goldblatt et al., Apr. 20, 2004, discloses methods for making graft copolymers, in an extruder, wherein at least one of the reactants is introduced in the presence of a polar solvent [abstract]. The extrusion process with reactant introduction in a solvent is said to allow for greater reaction efficiency in utilization of raw materials. The polar solvent is preferably water.
U.S. Pat. No. 8,410,031, Meessen et al., Apr. 2, 2013, discloses a process for preparing an imidized polymer in a mixing or kneading device, by a reaction in the presence of an acid of a mixture containing a polymer having anhydride groups or derivatives thereof and an aromatic polyamine compound. At least one of the amine groups is a primary amine. A purification zone in an extruder is a region where the solvent, unreacted reagents, by-products, co-products and other volatile impurities from the reaction are removed from the polymer.
U.S. Pat. No. 7,981,847, Goldblatt et al., Jul. 19, 2011, discloses lubricating oil compositions containing graft copolymers. The graft copolymer contains one or more ethylenically-unsaturated aliphatic or aromatic, nitrogen- and oxygen-containing graftable monomers grafted to a polyolefin. The monomer may, but need not be, recovered from the product mixture. A graftable monomer comprising the reaction product of maleic anhydride and 4-aminodiphenylamine is disclosed.
U.S. Pat. No. 5,663,126, Boden et al., Sep. 2, 1997, discloses polar grafted polyolefins containing an ethylenically-unsaturated nitrogen- or oxygen-containing graftable monomer such as N-vinylimidazole. The reaction can be carried out by providing a melted reactant composition in an extruder or other polymeric mixer substantially in the absence of a solvent. The grafting may also be carried on in the presence of a solvent having less than about 15% by weight of reactive aromatic constituents; the polyolefin is disclosed as dissolved in a solvent. The graftable monomer may be added neat, in solid or molten form, or cut back with a solvent. The solvents include volatile solvents which are readily removable from the grafted polyolefin after the reaction is complete; alternatively, they may be base oils.
U.S. Pat. No. 5,565,161, Auda et al., Oct. 15, 1996, discloses a process for producing a functionalized thermoplastic polymer. Multiple sequential chemical reactions are carried out in an extruder. In an example, an ethylene-propylene copolymer is sequentially maleated and then imidized in a single reactor-extruder. A controlled amount of water is injected into the extruder and subsequently removed by a vacuum vent. Feed of water is said to lead to less colored products.
WO 2006/084698, DSM (Meessen), Aug. 17, 2006, discloses a highly grafted multifunctional olefin polymer by reacting an olefin copolymer with an olefinic carboxylic acid acylating agent, preferably in the absence of a hydrocarbon solvent in, e.g., an extruder. The polymer will be dissolved in a Group I, II, III or IV oil and reacted with a specific polyamine. In an example, pelletized intermediate product is mixed with Group I oil and reacted with an amine such as N-phenyl-1,4-phenylenediamine which may be dissolved in an ethoxylated lauryl alcohol surfactant.
There remains a need for a convenient method for imparting amine, amide, imide, or other nitrogen or polar functionality to a viscosity modifier polymer by a reaction of a primary or secondary amine with the viscosity modifier polymer. It is often desirable to use a melt process for the polymer, so that the polymer does not need to be dissolved in a solvent such as mineral oil. This is often accomplished by providing the polymer in a melted (molten) state by processing it in an extruder or other melting and mixing device, and, indeed, acylated hydrocarbon polymers may be conveniently prepared by extruder grafting processes. If a polymer such as an acylated copolymer is then to be reacted with an amine, such as an aromatic amine that is normally solid at room temperature, the amine must normally be supplied in a melted form at an elevated temperature. The equipment for maintaining a supply of melted amine may be cumbersome, and the amine itself may be subject to undesirable thermal or oxidative degradation if it is maintained at elevated temperature for an extended period of time. However, if the amine is provided as a room-temperature solution in a relatively volatile solvent, the solvent normally must be removed from the mixture after reaction is complete. If it is provided as a mixture with a non-volatile surfactant material, the surfactant may lead to problems with foaming upon subsequent contact with water as in an underwater pelletizer. If a mineral oil is used as a solvent, the degree of solubility of the relatively polar amine therein may be so low that a great excess of the mineral oil may be required in order to assure solubility.